Drying apparatus

ABSTRACT

A dryer, for drying moisture-containing webs, comprises a strayfield platen defined by a plurality of radio frequency electrodes arranged substantially on an arc and defining a path for a web to be dried, feed means for initially feeding a web to be dried through the dryer and extending along a path remote from the platen and additional heating means for initially directing a jet of a warm gas such as air on to the web to be dried.

United States Patent 72] Inventors Eric Wain Hilton; Neil Steadman, Buckden, both of England [21] Appl. No. 879,068 [22] Filed Nov. 24, 1969 [45] Patented Dec. 28, 1971 [73] Assignee Eastman Kodak Company Rochester, N.Y. [32] Priority Nov. 25, 1968 [3 3] Great Britain [31] 55,781/68 [54] DRYING APPARATUS 10 Claims, 2 Drawing Figs.

[52] US. Cl 34/1 [51] Int. Cl 801k 5/00 [50] Field of Search 34/1 [56] References Cited FOREIGN PATENTS 1,079,677 8/1967 Great Britain 34/l Primary Examiner-Charles Sukalo Auorneys-Walter O. Hodsdon and Robert F. Cody ABSTRACT: A dryer, for drying moisture-containing webs, comprises a stray-field platen defined by a plurality of radio frequency electrodes arranged substantially on an arc and defining a path for a web to be dried, feed means for initially feeding a web to be dried through the dryer and extending along a path remote from the platen and additional heating means for initially directing a jet of a warm gas such as air on to the web to be dried.

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filll. I I I I llllllllll l I I l I I I Ill! I v l I l llnlll ll I I I I llrlllJ A TTOfP/VEYS DRYING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention concerns a drying apparatus and particularly, but not exclusively, an apparatus for drying paper webs, for example, processed photographic prints, before glazing.

2. Description Relative to the Prior Art Hitherto it has been necessary, in drying processed photographic prints, in continuous strip form, to pass them through a drying box wherein hot air was supplied to remove moisture from the prints. Such drying took a considerable period of time and was the slowest step in a photofinishers continuous printing, color processing, and glazing department.

To obtain maximum efficiency, it is necessary to have the print drying time compatible with the printing or processing steps and this is only possible, in present day apparatus, by having a substantial length of processed prints being dried in a dryer in order to allow the prints to be exposed to a warm air drying system for the required length of time.

SUMMARY OF THE INVENTION it is an object of the present invention to provide a new form of drying apparatus enabling, for example, in a photographic processing house, the time taken to dry the prints to be at least commensurate with the time taken for the other processing and finishing steps, thereby enabling a continuous processing line to be established without the necessity of having an inordinately long dryer.

According to the present invention, there is provided a dryer, for drying moisture-containing webs, comprising a stray-field platen defined by a plurality of radio frequency electrodes arranged substantially on an arc and defining a path for a web to be dried, feed means for initially feeding a web to be dried through the dryer and extending along a path remote from the platen and additional heating means for initially directing a jet of a warm gas such as air on to the web to be dried.

If desired, a similar means may be provided for directing a jet of wann gas across the surface of the web to be dried, adjacent an exit of the drier.

Air feed means may be provided for passing air through the drier to an extractor of the drier. The air feed means may, in the drier of the present invention, draw its air supply from the cooling air used for cooling the driver of the radio frequency electrodes thereby forcibly cooling such driver and simultaneously providing warm air to the drier.

The means for initially feeding the web may comprise a continuous belt whereto a leading end of a web to be dried may be clipped. The continuous belt may pass over rollers defining a path of progression thereof remote from the path to be occupied by the web to be dried. The path of progression aforementioned may be defined, for the belt, by stub rollers of width only sufficient to support the belt.

Conveniently, the web drier provides several drying paths for respective webs to be dried and, located between adjacent web paths, feed means for initially feeding the webs through the drier.

The belt or belts constituting the feed means may be in the form of continuous nylon belts.

In a preferred embodiment, there is provided, adjacent an entrance to the drier, means for removing surplus moisture from the surface of the web to be dried. Such means preferably takes the form of an air knife for each surface of the web but a suction device, squeegee rollers or rotating brushes may be used.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatic transverse section of a drying apparatus according to the present invention, and

FIG. 2 is a plan view of the apparatus shown in FIG. 1 with a screening box removed therefrom.

As shown in the drawings, a drying apparatus constructed in accordance with the present invention comprises a housing which is constructed of a conductive metal so as to provide a continuous screen and prevent stray radiation of radiofrequency electromagnetic waves propogated by the drier.

Located within the drier are a plurality of radio frequency electrodes 11 arranged substantially in an arc and supported between insulating spiders (not shown), and constituting a platen 12 which is known in the art, conventionally, as a strayfield platen.

Located substantially at the radial center of the arc of the platen is a tuning coil 13 which may be adjustable in position to adjust the tuning of the platen as a whole to enhance the efficiency of the radio-frequency dryer. The radially outer surfaces of the electrodes 11 define a web path wherealong a web to be dried is passed.

An entrance roller 14 is located adjacent an entrance 15 of the housing and an exit guide roller 16 is located again adjacent an exit 17 from the housing. The rollers 14 and 16 each extend substantially the whole width of the dryer (see FIG. 2). Located above the rollers 14 and 16 are stub rollers 18 and 19 supported by the insulating spiders and, centrally of the dryer, a stub roller 20 also supported by the spiders. A guide roller 21 is shown immediately outside the entrance 15 to the dryer and similarly a guide roll is provided (but not shown) adjacent the exit of the dryer.

The rollers 21, l4, 18, 20, 19, and 16 and the exit guide roller (not shown) define a path for a continuous web feed means in the form of a nylon belt 22 which serves initially to feed a web to be dried through the apparatus. It is to be noted that the belt 22 is outside the field of the radio-frequency electrodes. This is because despite its low dielectric loss, it is necessary to keep such belt out of the radio-frequency field in order to avoid undue heating thereof.

Adjacent the entrance l5 and adjacent the exit 17, are provided respectively heaters 23, 24 which comprise appropriately screened louvres 25, a screening housing 26, a rodlike heater element 27 and which may comprise additionally, blower means for drawing air through the louvres 25 forcing it over the elements 27 and through an exit slot 28 so as to direct a jet or jets of air over the surface of a web to be dried.

The housing 10 also has an inlet aperture 29 and a chimney 30, both appropriately screened. Warm air exhausted from a cooling system of a driver of the radio-frequency electrodes, for example, a 3.5 kilowatt oscillator, passes through the housing to remove moisture from the web to be dried.

In operation, a web 31 to be dried has its leading end passed through a water-removing device 32 which is preferably in the form of a double air knife and is thereafter clipped by means of a laterally extending clip (not shown) to the belt 22. The belt 22 draws the web to be dried over the roller 21 beneath the roller 14, and thereafter along an intermediate path extending somewhere between the path defined by the rollers 18, 20, and 19, and the arcuate path defined by the platen. When the leading and of the web has reached, approximately, the stub roller 19, the web to be dried thereafter follows a path substantially the same as the arc defined by the surface of the platen. The belt 22 conducts the web to be dried beneath the roller 16 and through the exit 17 of the drier. Automatic declipping means may be provided at the exit of the dryer for unclipping the web to be dried from the belt 22. The dried web can them be fed to some further station of a continuous apparatus or may be reeled in the form of a dried web.

The water-removing means 32 may take the form of a suction device, an air knife (as mentioned above), a pair of squeegee rollers, or rotating brushes or sponges for removing surplus water from the surfaces of the web.

The track followed by the web, as opposed to that followed by the belt, can be more easily seen from FIG. 2 where it will be seen that, although the rollers 14 and 16 are continuous across the width of the apparatus, the rollers l8, l9, and 20 are merely stub rollers supported by the insulating spiders (not shown) which extend outwardly from the region of the platen.

The offset relationship of the belt path and the web path can also be seen from this figure wherein one of the belts 22 is located between each two adjacent web paths, indicated by webs 31 to be dried.

The belts 22 take the leading ends of the webs 31 to be dried through the apparatus by means of laterally extending clips secured to the belt and engaging the leading end of a web. it is also visible, in this figure, that the web 31 to be fried passes beneath the rollers 14 and 16 and then extends over, and generally in contact with, the radio-frequency electrodes 11 of the platen 12.

This figure also illustrates that several webs may be dried simultaneously and that they need not be of the same width. No adjustment is normally needed to the apparatus which runs at a constant input but a variable output depending upon the amount of water present in the webs to be dried. As is well known, the dielectric loss of the material in the radio-frequency field formed by the electrodes 11 alters the capacitance between these electrodes and the greater the amount of water (as opposed to paper), the greater the power used by the apparatus to dry the web.

The apparatus has been described in detail with particular reference to a preferred embodiment thereof, but it will be understood that variations may be made within the scope of the invention. For instance, the apparatus is particularly suitable for the drying of photographic prints which are exposed and processed in the form of continuous strips and which are subsequently to be glazed, also in the form of continuous strips. A radio-frequency dryer as described hereinabove is capable of drying such prints in a matter of 40 seconds. This compared extremely favorably with the time previously taken to dry photographic prints.

As is conventional with stray-field platens, adjacent electrodes-l1 are connected to opposite output terminals of the oscillator so that the field is generated between adjacent elements. This, additionally, means that the field extending around the electrodes does not extend very far from the armate path defined thereby. Thus, with the processed prints in close contact with the electrodes, maximum transfer of energy to the web to dry the same is achieved. However, it is possible to position the electrodes 1'! along two concentric arcuate paths with the web to be dried passing therebetween and resting on the inner electrodes of such arcuate paths.

It will also be appreciated, of course, that the removal of moisture-laden air from the apparatus of this invention may be carried out by suction only or may be effected by pressure by providing blower fans to cooi the oscillator and in each of the heat exchanger units 26, if desired, in addition to extractor fans (not shown) in the chimney 30. Other variations are possible within the scope of the present invention.

What is claimed is:

l. A dryer, for drying a moisture-containing web, comprising a stray-field platen defined by a plurality of radio-frequency electrodes arranged substantially on an arc and defining a path for and being in contact with a surface of a web to be dried, feed means for initially feeding a web to be dried through the dryer, said feed means extending through said dryer along a path remote from the platen, and means for directing a jet of a warm gas onto the web surface to be dried opposite the surface in contact with said electrodes.

2. A dryer as claimed in claim 1 wherein means, adjacent an exit of the dryer, is provided for directing a jet of wann gas across the surface of said web to be dried.

3. A dryer as claimed in claim 2 including a radio-frequency driver cooperative with said electrodes, and wherein said gas is air, and said means for directing a jet is arranged to draw air from around said driver of the radio-frequency electrodes, thereby forcibly to cool such driver and simultaneously to provide warm air to the dryer.

4. A dryer as claimed in claim 1 wherein the means for initially feeding the web comprises a continuous belt whereto a leading end of a web to be dried may be clip d.

5. A dryer as claimed in clarm 4 wherein t e continuous belt passes over rollers defining a path of progression therefore remote from the path to be occupied by a web to be dried.

6. A dryer as claimed in claim 5 wherein the path of progression is defined, for the belt, by stub rollers of respective widths only sufficient to support the belt.

7. A dryer as claimed in claim 1 wherein the web dryer provides several drying paths for respective webs to be dried and, located between adjacent web paths, respective common feed means for initially feeding the webs through the dryer.

8. A dryer as claimed in claim 4 wherein the belt constituting the feed means is in the form of continuous nylon belt.

9. A dryer as claimed in claim 8 including, adjacent an entrance to the dryer, means for removing surplus moisture from the surface of a web to be dried.

it). An apparatus as claimed in claim 9 wherein the removing means is in the form of an air knife for each surface of the web. 

2. A dryer as claimed in claim 1 wherein means, adjacent an exit of the dryer, is provided for directing a jet of warm gas across the surface of said web to be dried.
 3. A dryer as claimed in claim 2 including a radio frequency driver cooperative with said electrodes, and wherein said gas is air, and said means for directing a jet is arranged to draw air from around said driver of the radio frequency electrodes, thereby forcibly to cool such driver and simultaneously to provide warm air to the dryer.
 4. A dryer as claimed in claim 1 wherein the means for initially feeding the web comprises a continuous belt whereto a leading end of a web to be dried may be clipped.
 5. A dryer as claimed in claim 4 wherein the continuous belt passes over rollers defining a path of progression therefor remote from the path to be occupied by a web to be dried.
 6. A dryer as claimed in claim 5 wherein the path of progression is defined, for the belt, by stub rollers of respective widths only sufficient to support the belt.
 7. A dryer as claimed in claim 1 wherein the web dryer provides several drying paths for respective webs to be dried and, located between adjacent web paths, respective common feed means for initially feeding the webs through the dryer.
 8. A dryer as claimed in claim 4 wherein the belt constituting the feed means is in the form of continuous nylon belt.
 9. A dryer as claimed in claim 8 including, adjacent an entrance to the dryer, means for removing surplus moisture from the surface of a web to be dried.
 10. An apparatus as claimed in claim 9 wherein the removing means is in the form of an air knife for each surface of the web. 